> The content is pretty good but I think they missed the target audience pretty badly with that title and cover.

I'm in agreement with you. The cover art and title give the impression of a children's book or a coffee-table book or something "light and fun!". It's not a textbook, but it's much more than a fluffy lightweight children's book. Reading the sample chapter, I think the audience he should have targeted is anyone who liked the monthly magazine "Scientific American" (if you're old enough to remember that). Basically anyone who wouldn't mind being called a hacker, nerd, geek, or science fan. Which is still a huge audience.